In general, strong countries dominated weaker ones to promote their own national self-interest, out of economic, religious, cultural, or other reasons. It has been said that the three primary motives for establishing colonies were gold, God, and glory, but the main incentives were usually economic. .
A Economic Motives .
The colonizing country could control important markets for its exports (such as cotton products) and deny these markets to its competitors. Colonies were also important as sources of raw materials (such as raw cotton) and as opportunities for investment. A country often also increased its wealth by conquering another civilization and taking its riches or by exploiting the mineral wealth of another land. In the 16th century, for example, Spain became a rich and powerful country largely by plundering the riches of existing civilizations in the Americas and by seizing the area's mineral wealth through mining.
These practices were promoted by the policy of mercantilism that many European colonial powers adopted. Those who advocated mercantilism believed that exports to foreign countries were preferable both to trade within a country and to imports because exports brought more money into the country. They also believed that the wealth of a nation depended primarily on the possession of gold and silver. Mercantilists assumed that the volume of world wealth and trade was relatively static; so one country's gain required another's loss. According to this view, a colonial possession should provide wealth to the country that controlled it. Colonies were not supposed to compete with the mother country's home industries. Empires were closed systems, designed to keep competitors out.
To implement mercantilist policy, England passed legislation called the Navigation Acts that restricted its colonies to trading solely with the mother country. The acts also stipulated that goods imported or exported by English colonies in Africa, Asia, or America had to be shipped on vessels constructed by English shipbuilders and that at least three-quarters of the ships' crews had to be English.